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In-line three-dimensional holography of nanocrystalline objects at atomic resolution.

Chen FR, Van Dyck D, Kisielowski C - Nat Commun (2016)

Bottom Line: Resolution and sensitivity of the latest generation aberration-corrected transmission electron microscopes allow the vast majority of single atoms to be imaged with sub-Ångstrom resolution and their locations determined in an image plane with a precision that exceeds the 1.9-pm wavelength of 300 kV electrons.The method is compatible with low dose rate electron microscopy, which improves on signal quality, while minimizing electron beam-induced structure modifications even for small particles or surfaces.We apply it to germanium, gold and magnesium oxide particles, and achieve a depth resolution of 1-2 Å, which is smaller than inter-atomic distances.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering and System Science, National Tsing-Hua University, 101 Kuang-Fu Road, Hsin Chu 300, Taiwan.

ABSTRACT
Resolution and sensitivity of the latest generation aberration-corrected transmission electron microscopes allow the vast majority of single atoms to be imaged with sub-Ångstrom resolution and their locations determined in an image plane with a precision that exceeds the 1.9-pm wavelength of 300 kV electrons. Such unprecedented performance allows expansion of electron microscopic investigations with atomic resolution into the third dimension. Here we report a general tomographic method to recover the three-dimensional shape of a crystalline particle from high-resolution images of a single projection without the need for sample rotation. The method is compatible with low dose rate electron microscopy, which improves on signal quality, while minimizing electron beam-induced structure modifications even for small particles or surfaces. We apply it to germanium, gold and magnesium oxide particles, and achieve a depth resolution of 1-2 Å, which is smaller than inter-atomic distances.

No MeSH data available.


Related in: MedlinePlus

Column mass and focus histograms.(a) Germanium and (b) gold values are given in terms of single atoms. (c) MgO graphs refer to single molecules. Gaussian functions (red lines) are fitted to their width, which is given in form of an averaged 2*σ error bar in Table 1. In focus graphs, the number of atoms/molecules are converted into focus values by multiplication with their listed spacing in beam direction. For germanium and gold, a and b sites refer to the existing (110) surface corrugation. In case of MgO [100], a surface corrugation is absent but surfaces are either terminated by Mg or by O atoms.
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f3: Column mass and focus histograms.(a) Germanium and (b) gold values are given in terms of single atoms. (c) MgO graphs refer to single molecules. Gaussian functions (red lines) are fitted to their width, which is given in form of an averaged 2*σ error bar in Table 1. In focus graphs, the number of atoms/molecules are converted into focus values by multiplication with their listed spacing in beam direction. For germanium and gold, a and b sites refer to the existing (110) surface corrugation. In case of MgO [100], a surface corrugation is absent but surfaces are either terminated by Mg or by O atoms.

Mentions: Intentionally, we prepared a semiconductor, a metal and a ceramic sample by different techniques, namely by ion milling, thin film deposition and by electron beam-assisted processing, to obtain differently shaped objects. Amplitude and phase of their exit wave are shown in Fig. 2. Figure 2a displays a Ge [110] sample prepared from a bulk Ge single crystal by mechanical polishing and successive ion milling29, and one expects the creation of surface steps forming a wedge-shaped sample with shallow angles. The gold [110] sample was grown by physical vapour deposition on germanium30. After growth, the Ge substrate was etched away creating a free-standing metal sample with flat bottom and rounded top (Fig. 2b). It is emphasized that in this case twin boundaries and a dislocation core are included in the analysis to make the point that extended defects can be analysed by our procedure. Finally, the MgO sample originates from a polished MgO [001] single crystal, which was prepared in [100] cross-section31 and exposed to the high brightness electron beam at 300 kV for several minutes. In-situ observations revealed that the high-energy electron beam removes all sample preparation induced surface roughness and forces the formation of the stacked cube structure with one global [100] zone axis orientation (Fig. 2c). All images of Fig. 2 show crystals are suspended in the high vacuum of the electron microscope and the support films are not visible in the field of view. Moreover, we did not find any evidence for an attachment of residual gas molecules from the high column vacuum to the surfaces of the samples, as a cold N2 trap was used. The expected geometrical features including the presence of surface steps that, however, are not obvious in these images, except for contrast fluctuations in the amplitude image of the MgO [100] sample (Fig. 2c), which suggests the presence of MgO cubes. This information is simply masked by mixing sample shape with column length in the experimental images as described earlier. For their deconvolution we apply MPI and column mass measurements (Methods) to each atom column of the electron exit waves (Fig. 2), which provides the histograms of column mass and defocus values (Fig. 3). It is seen that all histograms reveal discrete sets of peaks, which are periodically spaced. Image simulations confirm that the incremental steps between adjacent peaks correspond to the addition of single atoms or molecules to atom columns with a periodic spacing in the beam direction set by the crystal structures of the materials. In a second process, we determine the confidence levels of these measurements by fitting Gaussians to the accumulation points (Fig. 3). This allows for an extraction of error bars that are given as 64.2% probability values (2σ values) of the measurements and are listed in Table 1.


In-line three-dimensional holography of nanocrystalline objects at atomic resolution.

Chen FR, Van Dyck D, Kisielowski C - Nat Commun (2016)

Column mass and focus histograms.(a) Germanium and (b) gold values are given in terms of single atoms. (c) MgO graphs refer to single molecules. Gaussian functions (red lines) are fitted to their width, which is given in form of an averaged 2*σ error bar in Table 1. In focus graphs, the number of atoms/molecules are converted into focus values by multiplication with their listed spacing in beam direction. For germanium and gold, a and b sites refer to the existing (110) surface corrugation. In case of MgO [100], a surface corrugation is absent but surfaces are either terminated by Mg or by O atoms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4759637&req=5

f3: Column mass and focus histograms.(a) Germanium and (b) gold values are given in terms of single atoms. (c) MgO graphs refer to single molecules. Gaussian functions (red lines) are fitted to their width, which is given in form of an averaged 2*σ error bar in Table 1. In focus graphs, the number of atoms/molecules are converted into focus values by multiplication with their listed spacing in beam direction. For germanium and gold, a and b sites refer to the existing (110) surface corrugation. In case of MgO [100], a surface corrugation is absent but surfaces are either terminated by Mg or by O atoms.
Mentions: Intentionally, we prepared a semiconductor, a metal and a ceramic sample by different techniques, namely by ion milling, thin film deposition and by electron beam-assisted processing, to obtain differently shaped objects. Amplitude and phase of their exit wave are shown in Fig. 2. Figure 2a displays a Ge [110] sample prepared from a bulk Ge single crystal by mechanical polishing and successive ion milling29, and one expects the creation of surface steps forming a wedge-shaped sample with shallow angles. The gold [110] sample was grown by physical vapour deposition on germanium30. After growth, the Ge substrate was etched away creating a free-standing metal sample with flat bottom and rounded top (Fig. 2b). It is emphasized that in this case twin boundaries and a dislocation core are included in the analysis to make the point that extended defects can be analysed by our procedure. Finally, the MgO sample originates from a polished MgO [001] single crystal, which was prepared in [100] cross-section31 and exposed to the high brightness electron beam at 300 kV for several minutes. In-situ observations revealed that the high-energy electron beam removes all sample preparation induced surface roughness and forces the formation of the stacked cube structure with one global [100] zone axis orientation (Fig. 2c). All images of Fig. 2 show crystals are suspended in the high vacuum of the electron microscope and the support films are not visible in the field of view. Moreover, we did not find any evidence for an attachment of residual gas molecules from the high column vacuum to the surfaces of the samples, as a cold N2 trap was used. The expected geometrical features including the presence of surface steps that, however, are not obvious in these images, except for contrast fluctuations in the amplitude image of the MgO [100] sample (Fig. 2c), which suggests the presence of MgO cubes. This information is simply masked by mixing sample shape with column length in the experimental images as described earlier. For their deconvolution we apply MPI and column mass measurements (Methods) to each atom column of the electron exit waves (Fig. 2), which provides the histograms of column mass and defocus values (Fig. 3). It is seen that all histograms reveal discrete sets of peaks, which are periodically spaced. Image simulations confirm that the incremental steps between adjacent peaks correspond to the addition of single atoms or molecules to atom columns with a periodic spacing in the beam direction set by the crystal structures of the materials. In a second process, we determine the confidence levels of these measurements by fitting Gaussians to the accumulation points (Fig. 3). This allows for an extraction of error bars that are given as 64.2% probability values (2σ values) of the measurements and are listed in Table 1.

Bottom Line: Resolution and sensitivity of the latest generation aberration-corrected transmission electron microscopes allow the vast majority of single atoms to be imaged with sub-Ångstrom resolution and their locations determined in an image plane with a precision that exceeds the 1.9-pm wavelength of 300 kV electrons.The method is compatible with low dose rate electron microscopy, which improves on signal quality, while minimizing electron beam-induced structure modifications even for small particles or surfaces.We apply it to germanium, gold and magnesium oxide particles, and achieve a depth resolution of 1-2 Å, which is smaller than inter-atomic distances.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering and System Science, National Tsing-Hua University, 101 Kuang-Fu Road, Hsin Chu 300, Taiwan.

ABSTRACT
Resolution and sensitivity of the latest generation aberration-corrected transmission electron microscopes allow the vast majority of single atoms to be imaged with sub-Ångstrom resolution and their locations determined in an image plane with a precision that exceeds the 1.9-pm wavelength of 300 kV electrons. Such unprecedented performance allows expansion of electron microscopic investigations with atomic resolution into the third dimension. Here we report a general tomographic method to recover the three-dimensional shape of a crystalline particle from high-resolution images of a single projection without the need for sample rotation. The method is compatible with low dose rate electron microscopy, which improves on signal quality, while minimizing electron beam-induced structure modifications even for small particles or surfaces. We apply it to germanium, gold and magnesium oxide particles, and achieve a depth resolution of 1-2 Å, which is smaller than inter-atomic distances.

No MeSH data available.


Related in: MedlinePlus